Hair loss is a problem faced by many men and women. It is believed that the average person has about 100,000 hairs on their head and it generally takes greater than 50% of hair loss to notice a visual perceptional difference. While it is normal to lose about 100 hairs a day, it is nearly impossible to keep track of the rate and degree of hair loss during a given period of time by counting hairs. The measurement of hair bulk is one way to determine ‘practical’ changes in areas of the scalp or in the same area of the scalp over time.
There are three phases of a hair growth cycle and they are not all in the same phase at any one given time. Growth phase (Anagen phase) lasts anywhere from 2 to 6 years. This is the phase where hair is actively growing at approximately 10 cm per year. 85-90% of hair is at the anagen phase at any given time. Transitional phase (Catagen phase) lasts about 2 weeks. This is the phase where the hair follicles shrink and prepare to enter the resting phase. Resting phase (Telogen phase) lasts about 1-6 months. This is the phase where hair does not grow and generally falls out. Most hairs are shed in this phase, but at the end of the cycle, hair follicles re-enter the growth phase to start the cycle over again. At any given time approximately 10-15% of the scalp hairs are at the telogen phase and contribute no bulk value to the areas of hair baring skin while in the telogen phase.
The distinguishing factor which differentiates permanent scalp hair loss from cyclical hair loss is that the population of hair and the bulk of that hair decreases gradually in the affected areas. These changes in men impacted by genetic balding result in a permanent loss of hair bulk and a reduction of hair population (hair density).
The permanent loss of hair is often confined to limited anatomical sites. In men, hair loss generally follows a series of patterns (often referred to as “Male Pattern Baldness” or “Androgenic Alopecia” and are characterized by a generally agreed upon terminology called the “Norwood Classification of Hair Loss”). In women, it follows variable patterns which are more difficult to characterize. The process of losing hair also occurs at different rates, over different periods of time, and at different ages, even in the same individual. Hair loss in women can be diffuse without a pattern or they can be confined to areas of the front, top or crown of the head. In men, permanent hair is immune to the impact of genetic patterned hair loss and these areas are confined to the back and sides of the head.
As hairs become diseased, individual hairs may go through physical changes often referred to as miniaturization. Miniaturization is the process where a normal thickness hair shaft becomes thinner and thinner over time, often due to the genetically determined effects of aging and/or androgenic hormones on the terminal (normal) hair follicle. The process of miniaturization is generally a slow process in genetic balding. Hair shafts may lose 10% of their diameter, then 20%, then 30% and so on. Each degree of increased miniaturization reflects further progression of the genetic balding process, and produces a visually thinning look. This thinning look reflects a loss of hair populations and hair shaft thickness, and the thinning therefore is the results of loss of hair bulk (mass). A more limited segment of the population may just lose hair without going through the miniaturization process. Instruments that measure numbers of hairs and miniaturization exist as detailed in U.S. Pat. No. 5,331,472 issued Jul. 19, 1994 and these instruments are in wide use today.
The ability to diagnose hair loss in its earliest stages is dependent upon the early diagnosis of miniaturization, when it occurs. It is difficult to obtain a practical, accurate record of these measurements and the difficulties are compounded by many aesthetic factors such as the contrast between hair and skin color, hair thickness, hair character (wavy vs. straight vs. curly), and hair length. As an example, for the same amount of hair loss, there will be a more dramatic visual effect for someone with thin straight black hair on light skin than someone with thick wavy blond hair on light skin. Realistically, hair loss is a subjective observation and even with density measuring tools, estimating hair bulk loss is impractical and limited. Socially detectable hair loss is generally not evident until more than 50% of hair bulk has been lost and as a result, many men and women do not seek out expert help until they see obvious evidence of balding with bare scalp showing.
When a doctor views the scalp hair with high magnification, the degree of miniaturization and the location of the miniaturization are critical to establishing (1) the diagnosis and (2) the rate of the balding process which progresses over time. Because miniaturization is a relative measurement at any one time (comparing finer hair to the thickest hair), it takes substantial experience before this measurement can be useful to the individual clinician. Without good metrics, even the experienced physician exercises considerable subjectivity in the assessment. For repeated and accurate measurements, a tattoo must be placed at the exact point where the hair will be measured over time. Any place other than that exact point, will produce unreliable metrics that have limited value in establishing a hair metric. In our experience, from examining and following tens of thousands of patients with the Hair Densitometer (U.S. Pat. No. 5,331,472 issued Jul. 19, 1994), we have found that assessing the degree of miniaturization has useful predictive value when identifying the problems of genetic hair loss has commenced. Estimating the changes in hair bulk associated with hair loss and in particular hair loss over time, is near impossible. The amount of miniaturization in each section of the scalp gives the physician an ability to guess the extent (what areas are impacted) and the phasing of the hair loss (mild, moderate, severe hair loss) at that exact location and only at that exact location. In men who show more and more areas of miniaturization over time, the genetic balding can be considered active. In men treated with medications such as finasteride (Propecia), if the miniaturization of hair is reduced or the hair count is increased and if the areas under study are tattooed, it can be assumed that the balding process is responding to medical therapy at that exact location.
More often than not, the benefits when seen are observed because hair bulk returns more towards the original normal hair bulk as recorded in photographs or reported by the patient as his subjective view of the benefits of his/her treatment. Thus, quantitative measurement of hair count and estimates of hair shaft bulk (based upon miniaturization) in many hairs, which should become an essential tool for monitoring or diagnosing hair loss, turns out to produce inaccurate and non repeatable measurements.
Although there are numerous instruments and devices available for visually measuring hair count and hair shaft thickness at any particular point in the scalp, there exists no standardized method or automated process or device to process the data such that hair bulk assessments can be measured accurately for different section of the scalp, or for the same section of the scalp over different time periods. As the balding or miniaturization process occurs in patterns, the ability to estimate hair bulk today is extrapolated by counting and characterizing hair by hair counts in limited areas where the hair is cut short to measure it. Today's devices can count and measure individuals hairs at a particular location or the sum of individual hairs in a particular field of view. Hair by hair measurements are prone to human error due to its tedious nature and the subjectivity of human observation in analyzing an image and are rarely repeatable because the area under measurement are not exactly in the same area as previous measured.